Patient controlled atrial shock therapy

ABSTRACT

An implanted cardiac device detects an atrial arrhythmia and provides periodically updated atrial arrhythmia status as long as the arrhythmia is ongoing. A patient may request an indication of ongoing atrial arrhythmia status from external to the patient using a patient activator. The patient activator may include a magnet for closing a reed switch in the implanted device to provide the request or may provide the request over a telemetry link to the implanted device. The implanted device may provide the requested atrial arrhythmia status and other information in the form of an audible tone produced by the implanted device or as a message telemetered from the implanted device to the patient activator. The patient activator may include a tone detector and display for providing a visual indication of the atrial arrhythmia status indication. The magnet activator may also be employed to request or withhold atrial shock therapy.

FIELD OF THE INVENTION

The present invention pertains generally to medical devices and moreparticularly to implantable medical devices such as devices formonitoring activity of the heart and providing electrical shock therapythereto including automatic implantable cardioverter defibrillatordevices for treating atrial arrhythmias and external patient operabledevices for monitoring and controlling the operation of such implantablemedical devices.

BACKGROUND OF THE INVENTION

Various types of medical devices are employed to monitor electrical orother activity of the heart and to provide therapy to the heart inresponse to the detection of irregular cardiac rhythms. Such devices maybe implantable beneath the skin of a patient, i.e., in the patient'schest. Such implantable devices include a hermetically sealed canistercontaining electronic circuitry for implementing the functions of thedevice, one or more electrodes implanted in one or more of the chambersof the heart, or in close proximity thereto, and leads for connectingthe electrodes to the circuitry within the device canister. The devicecircuitry includes circuitry for detecting electrical signals producedby the heart, which signals are picked up at the electrodes, along withcircuitry, typically implemented in a microprocessor, for analyzing thethus-detected cardiac signals. The device may also include circuitry forproviding therapy in the form of electric shock signals applied to theheart. Such signals are provided to the heart, via the leads andelectrodes mounted in the heart, in response to the detection of anirregular cardiac rhythm by the analysis circuitry based on the detectedcardiac activity signals. The implantable device may also include atransmitter/receiver, for transmitting cardiac activity and otherinformation to an external device for, e.g., storage and/or furtheranalysis, and for receiving information, such as programminginstructions, from the external device via, for example, an RF link.

An example of such an implantable cardiac device is an automaticimplantable cardioverter defibrillator (AICD) for treating atrialarrhythmias, e.g., atrial tachycardia, fibrillation, flutter, etc. (Thefunctionality of an atrial AICD may be combined with those of abradycardia pacemaker, ventricular defibrillator, etc.) Atrialarrhythmias are probably the most common cardiac arrhythmia. Althoughatrial arrhythmias are not usually life-threatening, patients withatrial arrhythmias generally experience palpitations of the heart, andmay experience dizziness or even loss of consciousness. Atrialarrhythmias, such as atrial fibrillation, also have been associated withstrokes and other conditions. Atrial arrhythmias can occur suddenly.Implantable atrial cardioverter defibrillators are programmed to detectthe onset of atrial arrhythmias and to provide an appropriate electricalshock therapy to the atria to terminate the atrial arrhythmia. Theatrial shock therapy to be provided may depend upon the type of atrialarrhythmia detected, e.g., atrial tachycardia versus atrialfibrillation. Shock therapy provided by an implantable atrialcardioverter defibrillator may include a relatively high voltage levelatrial defibrillation or cardioversion pulse, which is typicallydelivered to the atria in synchronism with a detected or pacedventricular activation, to terminate atrial fibrillation or flutter.Atrial antitachycardia pacing may be applied by the implantable deviceto terminate atrial tachycardia. Atrial antitachycardia pacing typicallyinvolves a train of pacing pulses applied to the atria at a rateslightly higher than the rate of the tachycardia.

Various systems and methods have been developed to allow patients havingimplanted atrial cardioverter defibrillators to monitor and control, toat least some degree, operation of the implanted device. For example,U.S. Pat. No. 5,490,862 describes an implantable atrial defibrillatorwhich may be programmed to operate in a patient activated mode ofoperation. In the patient activated mode, an atrial fibrillationintervention sequence is performed by the implanted device in responseto the receipt of a sequence command generated from external to thepatient. The sequence command may be generated, for example, by anexternal magnet applied by the patient to near the implantation site, toclose and then open a reed switch mounted in the implanted device andcoupled to the device microprocessor. The intervention sequence thusinitiated by the patient, when he believes he is experiencing an atrialarrhythmia, includes atrial fibrillation detection by the implanteddevice and, if atrial fibrillation is confirmed, the application ofcardioverting electrical energy to the atria.

U.S. Pat. No. 5,674,249 describes the use of a portable communicationdevice which allows a patient to monitor and control the operation of animplanted atrial defibrillator. The portable communication device, whichmay be dimensioned to be hand held by a patient, includes atransmitter/receiver for communicating with the implanted device via atelemetry (e.g., RF) link. In this system, an atrial fibrillationintervention sequence may be initiated in an implanted device inresponse to a sequence command generated from the portable communicationdevice. The patient may also use the portable communication device toprogram the implanted device into an automatic mode wherein theintervention sequence is initiated automatically at predetermined times.The handheld portable communication device receives an acknowledgmentsignal from the implanted device when a command signal sent from thecommunication device is received by the implanted device. The receipt ofthe acknowledgment signal by the portable handheld communication deviceis displayed to the patient on the device. The display includes adescription of the task being performed by the implanted device inresponse to the command signal sent by the patient. Thus, a patient isable to both monitor and control operation of an implanted cardiacdevice to some degree.

U.S. Pat. No. 5,999,851 describes an implantable atrial defibrillatorwhich includes an atrial fibrillation detection only mode of operation.In this mode, atrial fibrillation detection is initiated in theimplanted device by a command signal sent from an external patientoperated communication device, which is in communication with theimplanted defibrillator via a telemetry (e.g., RF) link. If atrialfibrillation is detected by the implanted atrial defibrillator, anappropriate signal is communicated to the patient operated communicationdevice, and a visual and/or audible message is provided by thecommunication device to the patient to indicate whether or not atrialfibrillation is detected. In this detection only mode, a further signalmust be provided from the communication device to the implanted deviceto initiate cardioversion therapy, preferably after continued atrialfibrillation is confirmed by the implanted device.

In each of the systems described above, atrial fibrillation detection,or atrial fibrillation detection followed by atrial shock therapy, ifrequired, may be initiated by a patient using an external communicationdevice. To monitor the progress of an ongoing atrial arrhythmia event insuch systems, a patient must repeatedly signal the implanted device toreinitiate atrial fibrillation detection. Furthermore, to both monitorthe status of an atrial arrhythmia detected by the implanted device andcontrol the providing of shock therapy to the atria by the implanteddevice a relatively complicated external communication device employinga telemetry link is used to provide a variety of control signals fromthe communication device to the implanted device.

What is desired is an atrial shock therapy system which allows a patientto monitor the status of an ongoing atrial arrhythmia event withoutrequiring repeated reinitiation by the patient of atrial arrhythmiadetection. Preferably, a relatively simple and inexpensive patientcontrolled activator or communication device may be employed by thepatient both to monitor atrial event status as determined by animplanted device as well as to control the providing of atrial shocktherapy by the implanted device.

SUMMARY OF THE INVENTION

The present invention provides a system and method which allows apatient with an implanted automatic implantable cardioverterdefibrillator to monitor the status of an atrial arrhythmia detected bythe implanted device and to control the providing of shock therapy tothe atria by the device. In accordance with the present invention, apatient employs an external activator communication device to request anindication of the status of an ongoing atrial arrhythmia event withoutrequiring repeated initiation of atrial event detection by the implanteddevice. The patient activator communication device may preferably beimplemented in a relatively simple and inexpensive manner and allow thepatient both to request atrial arrhythmia event status as well as tocontrol the providing of electrical shock therapy to the atria by theimplanted device to terminate an atrial arrhythmia event.

The present invention may be implemented in an implantable cardiacdevice, such as an automatic implantable cardioverter defibrillator,which provides atrial arrhythmia detection and electrical shock therapyto the atria to terminate such atrial arrhythmias. (The implantabledevice may also include ventricular arrhythmia monitoring andventricular shock therapy functionality and/or ventricular pacingfunctionality, as well as atrial pacing capability.) The implantablecardiac device includes signal detection circuitry, connected via leadsto electrodes positioned in the atria and, preferably, the ventricles ofthe heart, to detect electrical heart activity signals. An implanteddevice system processor monitors the output provided by the signaldetection circuitry to detect the occurrence of an atrial arrhythmia,e.g., atrial tachycardia, fibrillation, and/or flutter, using knownatrial arrhythmia detection algorithms. The implantable device includescardioverter/defibrillator circuitry, controlled by the deviceprocessor, for providing defibrillation shock therapy, and/orantitachycardia pacing, depending upon the type of atrial arrhythmiaidentified, to the atria via the leads and electrodes implanted in theheart. The implantable device is preferably also provided with atelemetry receiver/transmitter, coupled to the device processor, toallow the processor to transmit cardiac activity and other data to anexternal programmer device for storage and/or further analysis, and toreceive data, such as programming instructions, from the externalprogrammer device. The external programmer device is a relativelycomplicated device used by a physician to program the implanted deviceand query cardiac activity data therefrom.

In accordance with the present invention, a patient, having an implantedcardiac device in accordance with the present invention, is able tomonitor an atrial arrhythmia detected by the implanted device andcontrol the providing of atrial shock therapy by the implanted deviceusing a patient activator communication device. The patient activator ispreferably a relatively small, handheld device, which allows the patientto initiate a patient activation operation in the implantable device todetermine the status of an atrial arrhythmia event detected by theimplanted device (if any) as well as, preferably, to control theproviding of shock therapy to the atria by the implantable device toterminate the atrial arrhythmia event. The patient activator preferablyemploys a relatively simple mechanism for initiating a patientactivation operation. For example, the patient activator may include amagnet which, when placed near the implantation site of the implanteddevice, operates a reed switch in the implanted device, which is coupledto the implanted device processor, thereby to initiate a patientactivation operation.

In response to the receipt of a patient activation request, theimplanted device provides information indicating the status of anyongoing atrial arrhythmia detected thereby to the patient. For example,the implanted device may include a tone-producing circuit, for driving asmall speaker, which produces distinctive tones, audible to the patient,which indicate that the implanted device has received the patientactivation request and whether or not an atrial arrhythmia is ongoing.The implanted device continually monitors and updates the status of anongoing atrial arrhythmia event. Periodically, e.g., every ventricularcycle, the implanted device updates the tone, or other signal, producedby the implanted device, to indicate to a patient any change in thestatus of the atrial arrhythmia event, as long as the patient activationrequest is provided by the activator. Thus, information on the changingstatus of an atrial arrhythmia event is provided periodically to apatient, e.g., as long as the patient activator is positioned near theimplantation site. In accordance with the present invention, a patientis not required to reinitiate periodically atrial arrhythmia detectionby the implanted device in order to obtain current atrial arrhythmiaevent status information.

The implanted device may also provide other information to the patient,such as the availability of the implanted device to provide atrial shocktherapy, in response to the initiation of an activation request by thepatient using the patient activator. For example, different audibletones may be produced by the implanted device depending on both whetheror not an atrial arrhythmia event is occurring and/or whether or notatrial shock therapy is available.

The patient activator communication device may also provide a visualindication to the patient indicating the ongoing status of an atrialarrhythmia event and/or the availability of atrial shock therapy. Forexample, the patient activator device may include tone detectioncircuitry which detects the various tones produced by the implanteddevice in response to a patient initiated activation request. The tonedetection circuitry converts such tones into electrical signals, whichmay be analyzed by an activator processor, which, in turn, drives adisplay (e.g., an LED or lamp display) on the activator to provide aperiodically updated visual indication of atrial arrhythmia event statusand/or atrial shock therapy availability (as long as a patientactivation request is provided from the activator to the implanteddevice).

The patient activator communication device may also be employed tocontrol the providing of atrial shock therapy by the implanted device.For example, a patient activation operation, as described above, may beinitiated by positioning the patient activator device magnet near theimplantable device implant site for at least a relatively short initialduration (e.g., one second). In response to the presence of the patientactivator device, the implantable device provides an indication to thepatient (e.g., audibly) of the status of any detected atrial arrhythmiaevent. If the patient activator device is removed from near theimplantation site shortly thereafter (i.e., within less than a thresholdduration, e.g., seven seconds, from initial application of the activatorto the implantation site), atrial shock therapy will be withheld (i.e.,disabled), and no atrial shock therapy will be provided even though anatrial arrhythmia has been detected and atrial shock therapy isotherwise available. However, if the patient activation operation ismaintained for a longer period (e.g., more than the threshold duration),e.g., by maintaining the patient activator device magnet in position formore than the threshold duration, appropriate shock therapy (e.g.,synchronized cardioversion and/or antitachycardia pacing, depending uponthe nature of the atrial arrhythmia) will be requested and provided bythe implantable device, e.g., after the patient activator is removedfrom the implant site. If the patient activation operation is maintainedfor an even longer period (e.g., longer than a stop therapy thresholdduration, which may be, for example, sixty seconds), e.g., bymaintaining the patient activator device magnet in position for longerthan the stop therapy threshold duration, any shock therapy initiated inthe implantable device may be disabled (until the patient activator isremoved from position near the implant site and then replaced inposition near the implant site for at least the initial duration tore-initiate a patient activation operation). Thus, a patient is able toemploy a relatively simple and inexpensively implemented patientactivator (e.g., a magnet) to both monitor atrial arrhythmia eventstatus as detected by an implanted device as well as to control theproviding of shock therapy to the atria by the implanted device toterminate the detected atrial arrhythmia event. In more general terms,in accordance with the present invention, the presence of a patientactivation request may be used to request an atrial arrhythmia eventstatus indication from an implanted device, while the duration of thesame request signal is used to control the providing of atrial shocktherapy by the implanted device.

Although a relatively simple and inexpensive patient activator device,e.g., including a magnet, tone detector circuitry, a processor, and astatus display, may be employed in accordance with the presentinvention, a more complicated patient activator may also be used. A morecomplicated patient activator communication device may include areceiver/transmitter for communicating control signals to and receivingstatus information signals from the implanted cardiac device via atelemetry (e.g., RF) link with a corresponding receiver/transmitter inthe implanted device. Such a patient activator communication device mayinclude a patient input circuit, including buttons, switches, etc., forallowing a patient to signal via the telemetry link from the activatorto the implanted device to initiate a patient activation operation.Atrial arrhythmia event status information may be communicated, inresponse to receipt of the activation request by the implanted device,from the implanted device to the activator over the telemetry link. Suchstatus information may be displayed or otherwise presented in visual oraudible form to the patient by the activator device. The patientactivator may also employ telemetry to request and receive statusinformation from the implanted device regarding the availability ofatrial shock therapy, as well as to control the providing of atrialshock therapy by the implanted device.

Further objects, features, and advantages of the invention will beapparent from the following detailed description taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic block diagram of an exemplary implantable cardiacdevice for detecting atrial arrhythmias and providing electrical shocktherapy to the atria, and a patient activator communication device forcontrolling the implantable device to provide atrial arrhythmia eventstatus information to the patient and to control the providing of shocktherapy to the atria by the implantable device.

FIG. 2 is a more detailed schematic block diagram of an exemplarypatient activator communication device in accordance with the presentinvention.

FIG. 3 is flowchart diagram illustrating an exemplary method forobtaining updated atrial arrhythmia event status information from animplanted cardiac device in accordance with the present invention usinga patient activator communication device in accordance with the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An exemplary implantable cardiac device 10 which may be controlled by apatient activator communication device 12 to provide atrial arrhythmiaevent status and other information to a patient and to provide patientcontrolled atrial shock therapy in accordance with the present inventionis illustrated in, and will be described in detail with reference to,FIG. 1. Although described in detail herein with reference to animplantable device 10 having the primary function of detecting andtreating atrial arrhythmias, it should be understood that the presentinvention may be employed with an implantable device which also performsother functions, such as ventricular monitoring and therapy and singleor dual chamber bradycardia pacing.

The implantable cardiac device 10 includes a hermetically sealedcanister 14 which encloses circuitry for detecting and analyzing cardiacarrhythmias and for providing electrical shock therapy to treat sucharrhythmias. The circuitry within the canister 14 is connected via oneor more leads 16 to one or more electrodes 18 which are implanted in ornear the chambers of a patient's heart 20. The electrodes 18 pick upelectrical signals produced in the chambers of the heart 20 and provideelectrical contact for electrical pulses or shocks which are deliveredto the chambers of the heart 20 to pace or defibrillate/cardiovert theheart 20. Depending upon the specific applications and functionality ofthe implantable cardiac device 10, electrodes 18 may be positioned in ornear the atria, ventricles, or, preferably, both the atria andventricles of the heart 20. In an implantable cardiac device 10 inaccordance with the present invention for detecting atrial arrhythmias,and providing atrial shock therapy to terminate such atrial arrhythmias,for example, electrodes 18 are positioned in or near the atria, fordetecting atrial activity and providing atrial shock therapy to theatria, as well as in the ventricles, for detecting ventricular activity,e.g., for use in verifying the presence of atrial arrhythmias and insynchronizing the providing of atrial cardioversion shock pulses to theatria with ventricular events. A plurality of leads 16 may be requiredto connect the electrodes 18 positioned in the heart 20 to the circuitrywithin the device canister 14. As is known in the art, multipleelectrodes 18 may be coupled to the circuitry within the canister 14 viaa single one of the leads 16. The canister 14, leads 16, and electrodes18 are preferably designed such that the entire device 10 is implantablebeneath the skin of a patient.

The leads 16 connect the electrodes 18 positioned within the heart 20 tosignal detection circuitry 22 within the implantable device canister 14.The signal detection circuitry 22 may be implemented in a conventionalmanner to provide atrial and/or ventricular activity signals based onthe cardiac signals picked up at the electrodes 18. Conventional signaldetection circuitry 22 may include signal amplifiers and filters, andmay include, in addition, circuitry for detecting atrial and ventriculardepolarizations and for providing atrial and ventricular depolarizationdetection indication signals in response thereto, along with circuitryfor obtaining electrogram signals and for providing digitizedelectrograms from the cardiac signals detected at the electrodes 18.

The signals provided by the signal detection circuitry 22 are providedto an implantable device system processor 24. The system processor 24may be implemented, for example, as one or more conventionalmicroprocessors with associated memory 26. Memory 26 may be an integralpart of, or separated from, but coupled to, the processor 24. Memory 26is employed in a conventional manner to store data, such as cardiacactivity data, for analysis by the processor 24, as well as to store theprogramming instructions which control the functions performed by theprocessor 24. For example, programming instructions for implementing anatrial arrhythmia detection algorithm 28 by the processor 24, and foroperating the processor 24 to generate messages 30 indicative of thestatus of an atrial arrhythmia event detected by the implanted device10, the availability of atrial shock therapy, etc., may be stored inmemory 26. These functions will be described in more detail below. Ofcourse, other general and conventional programming instructions for theprocessor 24 may also be stored in memory 26.

The implantable cardiac device 10 also includes conventionalcardioverter/defibrillator circuitry 32 for applying electrical energyto the heart 20 via the leads 16 and electrodes 18 positioned in theheart. In response to the detection of an atrial arrhythmia by theprocessor 24, based on cardiac signals provided by the signal detector22, the processor 24 controls the cardioverter/defibrillator to provideelectrical shock therapy to the heart 20 to terminate the atrialarrhythmia event. The type of electrical shock therapy provided to theheart 20 may depend upon the type of atrial arrhythmia event identified.For example, the cardioverter/defibrillator circuitry 32 may becontrolled by the processor 24 to provide a relatively high voltagelevel atrial defibrillation pulse to the atria of the heart 20 toterminate an atrial fibrillation or flutter event. Such relatively highvoltage shock therapy is preferably provided in synchronism with adetected or paced ventricular event, in order to prevent the atrialshock therapy from initiating a more serious ventricular arrhythmia. Inresponse to the detection of a high-rate, but more regular, atrialarrhythmia, e.g., atrial tachycardia, the processor 24 may control thecardioverter/defibrillator circuitry 32 to provide atrialantitachycardia pacing to the atria to terminate the atrial arrhythmiaevent. Atrial antitachycardia pacing may typically include a rapidseries of atrial pacing pulses delivered to the atria via a pacing lead16 and one or more electrodes 18 positioned in or near the atria of theheart 20. Various atrial shock therapies are known to those skilled inthe art, and will not be described in further detail herein.

The implantable device 10 may include receiver/transmitter circuitry 34including an antenna coil 36. The receiver/transmitter 34 may beimplemented in a conventional manner to transmit data from the systemprocessor 24 out of the implanted device 10 to a remote programmerdevice 38. For example, cardiac activity data detected by the signaldetector circuitry 22 may be transmitted to the external programmerdevice 38 to be stored and analyzed therein in more detail than ispossible in the implanted device 10 itself. The receiver/transmitter 34may also receive programming instructions from the external programmerdevice 38 for, for example, programming operating parameters of theimplantable cardiac device 10. Communication between thereceiver/transmitter 34 and the external programmer device 38 may beimplemented in a conventional manner, e.g., via a telemetry (e.g., RF)link. It is noted that the external programmer device 38 is a relativelylarge and sophisticated device which is typically employed by aphysician to monitor and control operation of the implantable device 10.

In accordance with the present invention, the implantable cardiac device10 may also include a reed switch 40 mounted therein and coupled to thesystem processor 24. As will be discussed in more detail below, the reedswitch 40 is operated (closed or opened) by the application of amagnetic field near the site of implantation in a patient of theimplantable cardiac device 10. The system processor 24 detects theoperation of the reed switch 40 as a patient activation request. Inresponse to the patient activation request, the system processor 24initiates a patient activation operation to provide an indication to thepatient of atrial arrhythmia event status and atrial shock therapyavailability, and to allow the patient to control the delivery of atrialshock therapy, as will be described in more detail below.

In accordance with the present invention, the implantable cardiac device10 may preferably also include tone generation circuitry 42. The tonegeneration circuitry 42 may be implemented in a conventional manner, andis controlled by the system processor 24 to drive a small speaker 44 toproduce different tones of sufficient volume to be audible by a patientin which the implantable device 10 is implanted. As will be discussed inmore detail below, the tones produced by the tone generation circuitry42 and speaker 44 may be used to indicate to a patient the status of anongoing atrial arrhythmia event and the availability of atrial shocktherapy.

The implantable cardiac device 10 also includes a battery 46, whichprovides power for the processor 24 and other circuit components of theimplantable cardiac device 10.

The circuitry for implementing the signal detector 22, processor 24,cardioverter/defibrillator 32, receiver/transmitter 34, tone producer42, and other functions of the implantable cardiac device 10 may beimplemented in a conventional manner using analog or digital circuitry,including one or more microprocessors, or any combination thereof. Aswill be known to those skilled in the art, functions performed by thesignal detector 22, cardioverter/defibrillator 32, receiver/transmitter34, and tone producer 42, may be performed by independent analog and/ordigital circuitry, as suggested by the illustration of FIG. 1, or may beimplemented in one or more processors 24, or with a combination ofindependent circuits and one or more processors.

In accordance with the present invention, a patient in which theimplantable cardiac device 10 is implanted may employ a patientactivator communication device 12 to request an indication from theimplanted cardiac device 10 of the status of atrial arrhythmia eventsdetected by the implanted device 10 and the availability of atrial shocktherapy, as well as to control the providing of atrial shock therapy bythe implanted device 10. The patient activator 12 is preferably designedto be portable, and is preferably small in size and able to be heldeasily in the hand and manipulated by a patient. Various componentswhich may be implemented in an activator 12 in accordance with thepresent invention are illustrated schematically in FIG. 2.

The activator 12 may preferably include a magnet 48 mounted therein. (Inits simplest form, a patient activator 12 in accordance with the presentinvention may be implemented with a magnet 48 alone). When the patientactivator 12 is positioned near the implant site of the implantabledevice 10 the magnetic field generated by the magnet 48 in the activator12 operates the reed switch 40 coupled to the processor 24 in theimplantable device 10. Operation of the reed switch 40 in this mannerfor at least a minimal period of time, e.g., one second, is recognizedby the implanted device processor 24 as a patient activation requestwhich initiates a patient-activation operation by the processor 24.During the patient-activation operation, the processor 24 employs amessage generator function 30 to generate a status message which isprovided to the patient to indicate the status of atrial arrhythmiaevents which are identified by the processor. Atrial arrhythmia eventstatus messages may be provided to the patient, as described above, bycontrolling tone generation circuitry 42 in the implantable device 10 togenerate a tone audible to the patient to indicate the status of anatrial arrhythmia event.

The atrial arrhythmia event status message generated by the implantabledevice 10 may also preferably be provided in a visual form to thepatient, e.g., in a visual display provided on the patient activator 12.For example, the activator 12 may include tone detection circuitry 50.The tone detection circuitry 50 may be implemented in a conventionalmanner to detect the tones produced by the tone generation circuitry 42in the implantable cardiac device 10 and to generate electrical signalsin response thereto. The electrical signals generated by the tonedetection circuitry 50 in the activator 12 are provided to an activatorprocessor 52, which decodes the signals provided by the tone detectioncircuitry. The activator 12 also includes conventional display circuitry54. The display circuitry 54 is driven by the activator processor 52, inresponse to the signals received from the tone detection circuitry 50,to provide a visual indication to the patient of the atrial arrhythmiaevent status indication provided by the implantable cardiac device 10.For example, the display circuitry 54 may include one or more LEDs orlamps 56 which are illuminated in a conventional manner to indicate,e.g., the receipt of a patient activation request by the implanteddevice 10, the presence or absence of an atrial arrhythmia event, theavailability of atrial shock therapy, etc., as will be described in moredetail below.

As an alternative to the magnet 48, for providing an activation requestto the implanted cardiac device 10, and tone detector circuitry 50, fordetecting atrial arrhythmia event status indication messages provided bythe implanted device 10, the activator 12 may include conventionalreceiver/transmitter circuitry 58, including an antenna 59. Theactivator receiver/transmitter 58 may be implemented in a conventionalmanner, and may be coupled to the receiver/transmitter 34 (or anothersimilar circuit) in the implanted device 10, via a telemetry (e.g., RF)link, to both provide patient activation request signals to and receivestatus information from the implanted cardiac device 10. The activatorreceiver/transmitter 58 is coupled to, and controlled by, the activatorprocessor 52. Patient input circuitry 60 is preferably also provided inthe activator 12 and coupled to the activator processor 52. Theactivator input circuitry 60 may include conventional buttons, switches,dials, etc., and related electronic circuitry. A patient employs theactivator input circuitry 60 to initiate a patient activation operationin the implanted device 10. For example, the patient may push a buttonon the activator 12, which is part of the input circuitry 60, to requestthe status of an ongoing atrial arrhythmia. A signal generated by theactivator input circuitry 60 is received by the processor 52 which, inturn, generates a command signal requesting, e.g., an updated atrialarrhythmia status indication from the implanted device 10. This commandmessage is, in turn, provided to the activator receiver/transmitter 58,to be transmitted to the implanted device 10, e.g., via thereceiver/transmitter 34 therein, over the telemetry link. The receivedcommand signal is, in turn, processed by the implanted device processor24. In response to the request, a message indicating, e.g., atrialarrhythmia event status, is generated by the implanted device processor24, and provided to the implanted device receiver/transmitter 34 fortransmission back to the activator 12. The status message is received bythe activator receiver/transmitter 58 and provided to the activatorprocessor 52. The activator processor 52 processes the atrial arrhythmiastatus indication message received from the implanted device 10, andgenerates therefrom an indication of ongoing atrial arrhythmia status,which, e.g., may be presented to the patient by controlling theactivator display 54. Of course, the indication may be providedvisually, audibly, and/or in any other manner to a patient on theactivator 12. Other status information, such as shock therapyavailability, may also be requested from the implanted device 10 usingthe input 60 and receiver/transmitter circuitry 58. Such telemetrycircuitry may also be employed to request or withhold the providing ofshock therapy by the implanted device 10. It should be noted that apatient activator 12 will typically include either thereceiver/transmitter 58 and input circuitry 60 or a magnet 48 and tonedetector 50, but may include both systems, as illustrated in FIG. 2.

An exemplary process in accordance with the present invention forproviding patient control and monitoring of atrial shock therapyprovided by an implanted cardiac device 10 will now be described indetail with reference to the exemplary flowchart diagram of FIG. 3. Inaccordance with the present invention, the implanted device 10 maydetermine automatically at 64 the presence or absence of an atrialarrhythmia, e.g., atrial tachycardia, fibrillation, or flutter, withouta specific request to do so from external to the patient. For example,conventional methods may be used by the implanted device processor 24 tomonitor ventricular and/or atrial activity detected by the signaldetector 22 to determine the likelihood of the occurrence of an atrialarrhythmia. If conditions indicate that an atrial arrhythmia is likely,the processor 24 may employ one or more conventional atrial arrhythmiadetection algorithms 28 to determine if an atrial arrhythmia isoccurring, and the nature of the arrhythmia.

The implanted device processor 24 also continually checks for thereceipt of an activation request from the patient activator 12 at 66. Asdescribed above, such a request may be provided by a magnet 48 in theactivator 12 positioned near the implanted device 10, to operate thereed switch 40, which, in turn, is detected by the processor 24.Alternatively, an activation request signal may be sent to the implanteddevice processor 24 via a telemetry link established between theactivator receiver/transmitter 58 and the implanted devicereceiver/transmitter 34. If an activation request 66 is not detected bythe implanted device processor 24, the processor 24 continues to monitorthe status of a detected atrial arrhythmia 64, continually updatingongoing atrial arrhythmia status, while continually checking for receiptof an activation request 66, until such a request is received.

If an activation request 66 is received by the implanted deviceprocessor 24, the processor 24 generates a confirmation message orsignal at 68, e.g., employing the message generator function 30 storedin memory 26, to provide confirmation to a patient that the activationrequest has been received by the implanted device 10. The confirmationsignal or message may be in the form of a message transmitted from theimplanted device receiver/transmitter 34 to the activatorreceiver/transmitter 58 and displayed or otherwise presented on theactivator 12 by the activator processor 52, e.g., on the activatordisplay 54. Alternatively, the confirmation signal may be provided as atone produced by the tone producer 42 and speaker 44 in the implanteddevice 10 and audible by the patient, and/or received by the tonedetector 50 in the activator 12 and translated to a visual signaldisplayed on the activator display 54.

The implanted device processor 24 then determines the current updatedstatus 70 of any atrial arrhythmia which may be occurring in thepatient's heart 20 and which has been detected by the implanted device10. If an atrial arrhythmia is occurring, the current status of theatrial arrhythmia is indicated to the patient at 72. If no arrhythmia isoccurring, this fact may also be indicated at 74, or simply no positiveindication of atrial arrhythmia is provided. The indication of thecurrent status of an atrial arrhythmia may be generated by the implanteddevice processor 24 employing the message generator function 30. Themessage indicating the status of an ongoing atrial arrhythmia may beprovided via the implanted device receiver/transmitter 34 and activatorreceiver/transmitter 58 to the activator 12 for display or otherpresentation thereon. Alternatively, the status of an ongoing atrialarrhythmia may be provided as an audible tone generated by the implanteddevice tone producer circuitry 42 and speaker 44, and audible to thepatient and/or received by the activator tone detector 50 and translatedinto a visual display on the activator 12.

After providing an indication to a patient of the current ongoing statusof an atrial arrhythmia, the processor 24 may return to monitoring andupdating the status of the atrial arrhythmia 64 and waiting for asubsequent activation request 66 from the activator 12. As long as anactivation request 66 is active, e.g., as long as the patient activator12 is in position to operate the reed switch 40, the implanted deviceprocessor 24 may provide automatically periodically updated atrialarrhythmia status indications to the patient in the manner described.Such updated status indications may be provided automatically, as longas the activation request 66 is active, at each occurrence of a selectedcardiac event, e.g., a ventricular event.

The implanted device processor 24 may also determine whether atrialshock therapy is available at 76, and provide an indication of atrialshock therapy availability to the patient at 78 and 80, e.g., in theform of a message transmitted from the implanted device 10 to theactivator 12 via a telemetry link, and/or as an audible tone. Forexample, shock therapy may be indicated as available if severalpredetermined conditions are satisfied. Such conditions may include, forexample, the presence of an ongoing atrial arrhythmia, the programmingON of shock therapy by a physician (using the programmer 38), the factthat shock therapy had not just been attempted for the ongoing atrialarrhythmia event, and the satisfaction of one or more verificationconditions, such as a detected atrial rate exceeding the detectedventricular rate, thereby confirming an atrial only arrhythmia. Otherconditions for determining whether or not shock therapy is availablemay, of course, also be employed.

It should be understood that not all of the steps illustratedschematically in FIG. 3 need be performed, and the steps illustrated maybe performed in a different order, in accordance with the presentinvention. For example, the steps of confirming an activation request68, indicating the presence or absence of an atrial arrhythmia 72, 74,and indicating the availability of shock therapy 78, 80 may be performedessentially simultaneously. These three pieces of information may beprovided to a patient using a minimal number of three distinctivelydifferent tones produced by the tone producer 42 and speaker 44. A firsttone may indicate that there is no ongoing atrial arrhythmia (and thusthat atrial shock therapy is not available). A second tone may indicatethat there is an ongoing atrial arrhythmia, but that atrial shocktherapy is not available. A third tone may indicate that there is anongoing atrial arrhythmia, and that atrial shock therapy is available.The production of any tone by the implanted device 10 confirms that anactivation request has been received thereby from the activator 12.

An important feature of the present invention, as illustrated in FIG. 3,is that the determination of the status of an atrial arrhythmia by theimplanted device processor 24 is performed automatically by theprocessor 24 independently of the receipt of an activation request froma patient. As along as an atrial arrhythmia is ongoing, the processor 24continues to monitor and update the status of the atrial arrhythmiaperiodically, e.g., at each occurrence of a selected cardiac, e.g.,ventricular, event. Thus, the current status of an ongoing atrialarrhythmia is readily available to be presented to a patient on requestusing the activator 12. Reinitiation of atrial arrhythmia detection bythe implanted device processor 24 is not required each time the patientrequests an atrial arrhythmia status indication update.

A patient informed as to the ongoing status of an atrial arrhythmiausing a system and method in accordance with the present inventionpreferably is able to employ such information to control the operationof the implanted device 10 to provide atrial shock therapy. For example,a patient may feel the onset of what he may believe to be an atrialarrhythmia. By use of the activator device 12, the patient is able toconfirm whether or not an atrial arrhythmia is occurring. The activator12 may then also be employed to request the implanted device 10 toproceed with providing atrial shock therapy to terminate the atrialarrhythmia (if such shock therapy is indicated as being available), orto withhold the providing of such therapy by the implanted device 10.For example, a patient may wish to withhold immediate atrial shocktherapy until the patient is better prepared for the therapy, at whichpoint the activator device 12 may be employed to initiate a shocktherapy request.

Patient controlled requesting and withholding of atrial shock therapymay be initiated by a patient using the activator input circuitry 60.The proper command signal may then be transmitted to the implanteddevice 10 over the telemetry link between activator receiver/transmitter58 and implanted device receiver/transmitter 34. Alternatively, therequesting and withholding of shock therapy may be performed using amore simple activator device 12 including a magnet 48. For example, asdiscussed above, by positioning the activator magnet 48 near theimplanted device 10, to operate the reed switch 40, a patient activationoperation is initiated in the implanted device 10. If the activationrequest is thus presented to the implanted device 10 for less than athreshold duration (e.g., less than seven seconds), the patient maythereby instruct the implanted device processor 24 to withhold theproviding of atrial shock therapy. If the activator 12 is maintained inposition for longer than the threshold duration (e.g., greater thanseven seconds), the implanted device processor 24 may be instructed toproceed with providing atrial shock therapy, either immediately or oncethe activator 12 is removed from position near the implanted device 10.Any shock therapy initiated in the implanted device 10 may be disabledby maintaining the activator 12 in position for at least a stop therapythreshold duration, which may be much longer than the threshold durationrequired to initiate therapy. For example, any shock therapy initiatedin the implanted device 10 may be disabled if the activator 12 ismaintained in position for longer than a stop therapy threshold durationof, e.g., sixty seconds. Shock therapy may be reinitiated following sucha stop therapy operation by removing the activator 12 from position nearthe implanted device 10 and then replacing the activator 12 in positionnear the implanted device 10 for at least the initial duration requiredto re-initiate a patient activation operation. (Preferably, all atrialshock therapy is disabled during application of the activator magnet 48near the implanted device 10.)

Of course, as discussed above, by positioning the activator magnet 48near the implanted device 10, the patient also requests an indication ofthe ongoing status of an atrial arrhythmia. Thus, a simple activatordevice 12 employing a magnet 48 may be used both to request an atrialarrhythmia status indication from an implanted device 10 in accordancewith the present invention (by the presence of the thus generatedactivation signal), as well as to control the operation of the implanteddevice 10 to provide atrial shock therapy (by the duration of thepresence of the thus generated activation signal). Since relativelycomplicated activator receiver/transmitter 58, input 60, and othercircuitry are not required, a relatively inexpensive and simple tooperate activator device 12 may thus be employed in accordance with thepresent invention to both monitor the status of an ongoing atrialarrhythmia and to control the providing of atrial shock therapy to treatthe arrhythmia.

It is understood that the present invention is not limited to theparticular exemplary embodiments and applications thereof illustratedand described herein, but embraces such modified forms thereof as comewithin the scope of the following claims.

1. A patient controllable atrial shock therapy system, comprising: animplantable device including: means for detecting an atrial arrhythmiaevent episode and updating automatically an atrial arrhythmia eventstatus periodically throughout the duration of a detected atrialarrhythmia event episode; means for detecting a patient activationrequest originating from external to the implantable device; and meansfor generating a message indicating to a patient the periodicallyupdated ongoing atrial arrhythmia event status in response to detectionof the patient activation request.
 2. The patient controllable atrialshock therapy system of claim 1 wherein the means for detecting theatrial arrhythmia event episode and updating automatically the atrialarrhythmia event status includes means for detecting atrial arrhythmiaevent episodes selected from the group of atrial arrhythmias consistingof atrial tachycardia and atrial fibrillation.
 3. The patientcontrollable atrial shock therapy system of claim 1 wherein the meansfor detecting the atrial arrhythmia event episode and updatingautomatically the atrial arrhythmia event status includes means forupdating atrial arrhythmia event status periodically at each occurrenceof a selected cardiac event occurring throughout the duration of adetected atrial arrhythmia event episode.
 4. The patient controllableatrial shock therapy system of claim 3 wherein the means for detectingthe atrial arrhythmia event episode and updating automatically theatrial arrhythmia event status includes means for updating atrialarrhythmia event status periodically at each occurrence of a ventricularevent occurring throughout the duration of a detected atrial arrhythmiaevent episode.
 5. The patient controllable atrial shock therapy systemof claim 1 wherein the means for detecting the patient activationrequest includes a reed switch responsive to a magnetic field to operatethe reed switch to provide the patient activation request.
 6. Thepatient controllable atrial shock therapy system of claim 5 wherein themeans for generating the message generates messages indicating theperiodically updated arrhythmia event status as long as the magneticfield operates the reed switch.
 7. The patient controllable atrial shocktherapy system of claim 1 wherein the means for generating the messageincludes means for generating messages indicating the periodicallyupdated arrhythmia event status as long as the patient activationrequest is detected.
 8. The patient controllable atrial shock therapysystem of claim 1 wherein the means for generating the message includesmeans for generating an audible tone indicating the periodically updatedarrhythmia event status.
 9. The patient controllable atrial shocktherapy system of claim 1 wherein the means for detecting the patientactivation request includes a reed switch responsive to a magnetic fieldto operate the reed switch to provide the patient activation request,wherein the means for generating the message generates the messageindicating the periodically updated arrhythmia event status in responseto operation of the reed switch, and wherein the means for generatingthe message includes means for generating an audible tone indicating theperiodically updated arrhythmia event status, and further comprising ahand-held activator including: a magnet for generating the magneticfield to operate the reed switch when the activator is positioned nearthe implantable device; means for receiving the audible tone indicatingthe periodically updated arrhythmia event status and converting theaudible tone indicating the periodically updated arrhythmia event statusinto an electrical signal indicating the periodically updated arrhythmiaevent status; and means responsive to the electrical signal indicatingthe periodically updated arrhythmia event status for displaying on theactivator a visual indication of the periodically updated arrhythmiaevent status.
 10. The patient controllable atrial shock therapy systemof claim 1 wherein the means for detecting the patient activationrequest includes a patient activation request receiver adapted toreceive a patient activation request signal, wherein the implantabledevice comprises additionally a status message transmitter responsive tothe means for generating the message for transmitting a status messageindicating the periodically updated arrhythmia event status, and furthercomprising a hand-held activator including: a patient activation requesttransmitter for transmitting a patient activation request signal to bereceived by the patient activation request receiver; a status messagereceiver adapted to receive the status message indicating theperiodically updated arrhythmia event status from the status messagetransmitter; and means responsive to the status message received by thestatus message receiver for displaying on the activator a visualindication of the periodically updated arrhythmia event status.
 11. Apatient controllable cardiac shock therapy system, comprising: animplantable device including: means for detecting a cardiac arrhythmiaand providing a cardiac arrhythmia event status; means for detecting apatient activation request originating from external to the implantabledevice; and means for generating audible tone messages within theimplantable device indicating the cardiac arrhythmia event status inresponse to detection of the patient activation request.
 12. The patientcontrollable cardiac shock therapy system of claim 11 further comprisingan external activator creating a magnetic field representative of thepatient activation request, and wherein the means for detecting thepatient activation request detects the magnetic field.
 13. The patientcontrollable cardiac shock therapy system of claim 12 wherein the meansfor detecting the patient activation request comprises a reed switchoperating in response to the magnetic field.
 14. The patientcontrollable cardiac shock therapy system of claim 11 further comprisingan external activator including an activator receiver/transmitter totransmit the patient activation request, and wherein the means fordetecting the patient activation request comprises an implantable devicereceiver/transmitter to receive the patient activation request.
 15. Asystem comprising: an implantable device including: an arrhythmiadetector to detect an arrhythmia event episode and provide an arrhythmiaevent status during the detected arrhythmia event episode; a switchoperating in response to a magnetic field representative of an externalactivation request; and an implantable device processor coupled to theswitch to detect the external activation request, the implantable deviceprocessor generating a message indicative of the arrhythmia event statusin response to the external activation request; and a patient controlledhand-held external activator adapted to provide the magnetic fieldrepresentative of the external activation request.
 16. The system ofclaim 15 wherein the arrhythmia detector comprises an atrial arrhythmiadetector.
 17. The system of claim 15 wherein the switch comprises a reedswitch, and wherein the external activator comprises a magnet generatingthe magnetic field representative of the external activation request.18. The system of claim 17 wherein the implantable device furthercomprises a tone producer coupled to the implantable device processor,the tone producer adapted to generate an tone indicative of thearrhythmia event status.
 19. The system of claim 18 wherein theimplantable device further comprises a speaker coupled to the toneproducer.
 20. The system of claim 18 wherein the external activatorfurther comprises: a tone detector adapted to detect the tone; and anactivator processor coupled to the tone detector, the activatorprocessor adapted to decode the detected tone.
 21. The system of claim18 wherein the external activator further comprises a display, coupledto the activator processor, to provide a visual indication of thearrhythmia event status.